Theresa May has sustained the heaviest parliamentary defeat of any British prime minister in the democratic era after MPs rejected her Brexit deal by a resounding majority of 230.
The Labour leader, Jeremy Corbyn, immediately moved to sieze the initiative, tabling a vote of no confidence in the government.
“This is a catastrophic defeat. The house has delivered its verdict on her deal. Delay and denial has reached the end of the line,” he said.
Brexit-supporting Conservatives joined with opposition parties and the Democratic Unionist party to trounce the government in the “meaningful vote”, which the prime minister delayed before Christmas in the vain hope of winning over waverers.
Following the defeat, May immediately invited a formal vote of no confidence in her own government, which she said would be voted on as soon as Wednesday.
The prime minister said the vote had not revealed what kind of deal MPs would be willing to support so if she won the vote of no confidence she would open talks with the DUP and “senior parliamentarians from across the house to identify what will be required to secure support”.
She said she would return to the Commons on Monday with a formal statement of how she will proceed.
May had begun the eighth day of the Brexit debate by making a last-ditch plea to colleagues to support her, warning them not to break their promise to the British people to deliver Brexit.
“This is the most significant vote that any of us will ever be part of in our political careers. After all the debate, all the disagreement, all the division, the time has now come for all of us in this house to make a decision. A decision that will define our country for decades to come,” she said.
“Together we can show the people we serve that their voices have been heard, that their trust was not misplaced.
Earlier in the day, as one Conservative backbencher after another stood up to slam her painstakingly negotiated withdrawal agreement in the House of Commons, it became clear that few had changed their mind – though whips urged MPs to abstain, rather than vote against the government.
May herself embarked on a last-ditch charm offensive on Tuesday, holding meetings with MPs including the European Research Group’s Steve Baker, who said the pair had held a “constructive and substantial conversation about the future”.
Speaking just before the vote, the Labour leader, Jeremy Corbyn, said “the prime minister has treated Brexit as a matter for the Conservative party, rather than the good of the whole country”.
He called the government’s efforts to steer Brexit through parliament “one of the most chaotic and extraordinary parliamentary processes” he had experienced in 35 years as an MP.
The attorney general, Geoffrey Cox, had earlier warned his colleagues that if they did not accept the deal, they risked condemning Britain to the chaos of a no-deal Brexit.
“It would be the height of irresponsibility for any legislator to contemplate with equanimity such a situation,” he said.
He argued that members of the public affected by no deal would say to MPs: “What are you playing at? What are you doing? You are not children in the playground. You are legislators, and this is your job.”
Both Labour and the Scottish National party withdrew amendments to the government’s motion at the last minute, to allow MPs a clean vote on the deal.
Just one amendment, tabled by the Brexiter John Baron and proposing a unilateral exit mechanism for the Irish backstop, was voted on and soundly defeated, by 600 votes to 24.
Throughout the turbulent period since she became prime minister in the wake of the shock referendum result in 2016, May has battled to unite her party over Brexit. Despite that, she faced a string of resignations, including two Brexit secretaries, David Davis and Dominic Raab, over the details of the deal.
The publication on Monday of letters between May and the European commission president, Jean-Claude Juncker, about the Irish backstop failed to win over Tory MPs who feared the UK could be trapped in a quasi-permanent customs union.
Downing Street said May opened her weekly cabinet meeting on Tuesday by saying the government was the servant of the people, and pledging to deliver the referendum result.
She will now come under intense pressure to cede control of the next steps in the Brexit process to parliament.
A spokesman for Donald Tusk, the president of the European council, said: “We regret the outcome of the vote, and urge the UK government to clarify its intentions with respect to its next steps as soon as possible.”
Government defeats by more than 100 votes are vanishingly rare; the only ones recorded in the past century occurred during the minority Labour government of 1924. Postwar, the only government defeats on a similar scale were by 89 in 1979, and 86 in 1978.